華東師大版初中九上2523銳角三角函數(shù)課件

1、特殊角的三角函數(shù)值表三角函數(shù)銳角正弦sin余弦cos正切tan3004506002123332222123213知識(shí)在于積累w用科學(xué)計(jì)算器求銳角的三角函數(shù)值,要用到三個(gè)鍵: w例如,求sin160,cos420, cot75045和sin630 5241的按鍵盤(pán)順序如下:w由于計(jì)算器的型號(hào)與功能的不同,按相應(yīng)的說(shuō)明書(shū)使用.按鍵的順序顯示結(jié)果Sin160Cos420Cot70045sin630 52410.27560.74310.39420.8979sin cos tansin16=cos42=tan70=sin66DMSDMS41=52DMS1DMS 45隨堂練習(xí)1 用計(jì)算器求下列各式的值:(

2、1)sin560, (3)cos200,(4)tan290, ,(2) sin15049按鍵的順序顯示結(jié)果Sin560Cos200tan290sin150 490.82900.93970.55430.2726sin56=cos20=tan29=sin15DMSDMS=49知識(shí)在于積累w已知三角函數(shù)值求角度,要用到三個(gè)鍵, 和第二功能鍵 和 . w例如,w由于計(jì)算器的型號(hào)與功能的不同,按相應(yīng)的說(shuō)明書(shū)使用.sinsinsincoscoscostantantan按鍵的順序顯示結(jié)果SinA=0.9816CosA=0.8607tanA=0.7410tanA=56.782ndf2ndf2ndfSinSin

3、Sin-1-1-10 0 0 . . .Sin-1=0.9816=78.99184039coscoscos-1-1-10 0 0 . . .coS-1=0.8607=30.60473007tantantan-1-1-10 0 0 . . .36.53844577tantantan-1-1-15 5 56 6 6 . . . 7 7 78 8 8tan-1=56.78=88.991020499 9 98 8 87 7 7= = =SinSinSin-1-1-1coscoscos-1-1-1tantantan-1-1-12ndf2ndf2ndf8 8 8 1 1 1 6 6 6 = = =6 6

4、6 0 0 0 7 7 7 = = =4 4 4 1 1 1 0 0 0 = = =2ndf2ndf2ndf2ndf2ndf2ndf2ndf2ndf2ndf熟能生巧071 302023 1835038 1646w1 根據(jù)下列條件求的大小:w(1)tan(1)tan=2.9888;(2)sin=2.9888;(2)sin=0.3957;=0.3957;w(3)cos(3)cos=0.7850;(4)tan=0.7850;(4)tan=0.8972.=0.8972.041 53542 如圖,根據(jù)圖中已知數(shù)據(jù),求AD.ABC55025020D0000,tan55.,tan2520tan25tan55

5、13.84,13.84xADxCDt ABDCDADxBCBDCDBDxxxAD00解：設(shè) 根據(jù)題意得:在t ACD中tan55在中，tan253 如圖,根據(jù)圖中已知數(shù)據(jù),求ABC其余各邊的長(zhǎng),各角的度數(shù)和ABC的面積.ABCaD0,cos ,sinsinsin,sincos1801sin(cos)2BDaaADaRt ACDACACBCaASaa解：過(guò)作 于點(diǎn)，在t ABD中,BDcos =同理：AB在中，asinasin同理：tantanasintan4 如圖,根據(jù)圖中已知數(shù)據(jù),求AD.ABCaD,tan.,tantantantantan,tantanxADxCDt ABDCDADxBCBDCDBDxxaax解：設(shè) 根據(jù)題意得:在t ACD中t